Long-term Time-share Guarantees are Necessary for Wireless LANs

Wireless local area networks (WLANs) based on a family of 802.11
technologies are becoming ubiquitous. These technologies support
multiple data transmission rates. Transmitting at a lower data rate (by
using a more resilient modulation scheme) increases the frame
transmission time but reduces the bit error rate. In non-cooperative
environments such as public hot-spots, individual nodes attempt to
maximize their achieved throughput by adjusting the data rate or frame
size used, irrespective of the impact of this on overall system
performance.

In a series of experiments, we demonstrate that the existing distributed
MAC protocol encourages non-cooperative nodes to use globally
inefficient transmission strategies that lead to degraded aggregate
throughputs. We also show that by establishing independence between the
allocation of the shared channel time and the strategies used by
individual nodes, an improved MAC protocol can lead rational but
non-cooperative nodes to make choices that increase aggregate
throughputs by as much as 30% under some conditions.